High-voltage rectifier



Dec. 19, 1950 o. H. SCHADE HIGH-VOLTAGE RECTIFIER 2 Sheets-She 2 FiledJuly 14, 1945 IN VENTOR 0/70 A! JCl/AD/F" BY )km ATTORNEY Patented Dec.19, 1950 2,534,532 HIGH-VOLTAGE RECTIFIER Otto H. Schade, West Caldwell,N. J assignor to Radio Corporation of of Delaware America, a corporationApplication July 14, 1945, Serial No. 605,131

I 19 Claims.

This invention relates to a new and useful electrical condenser of thehigh voltage high frequency type for use with high frequency industrialoscillators and the like.

An object of this invention is to provide an improved low cost lightweight condenser of the Leyden jar type wherein the inner electrodecoating exceeds the outer electrode coating in its physical length togive an increased creepage path by having an external uncoated skirt toaid in preventing corona discharge.

Another object of this invention is to provide a condenser which will bemade part of the actual circuit connections by combining the condenserwith high voltage rectifiers of the electron discharge type which arefrequently employed in a three stage voltage multiplier or triplingcircult.

Still another object of this invention is to provide an improvedelectrostatic condenser of the Leyden jar type which has increasedelectrical capacity for the same physical dimensions, and greatermechanical and electrical strength than those of the prior art.

A feature of this invention is the novel arrangement and shape of acondenser wherein the device has a re-entrant and reduced long neckedportion which permits telescoping and capacitive variation with adjacentcondenser units of similar shape.

Although electric condensers of the Leyden jar type are very old in theart, they are now infrequently used because of their bulk relative tothe unit of electrical capacity. Also corona, discharges causeionization and consequent heating and power loss in the air and glassdielectrics. The Leyden jars of the prior art frequently break down byan electrical puncture through the glass wall between the inner andouter electrodes at the end of each coating. This invention overcomesthe objection of the prior art condenser by providing a flask shapedcondenser having a reentrant portion, the outer portion of which isprovided in the central dome portion. An encircling skirt decreases thetendency to form corona discharge at the termination of the outsideelectrode. The wall thickness is increased and curved at the portionwhere the skirt joins the cylindrical portion of the flask at theterntination' of the outer electrode. The outer electrode itself isrounded over at the electrode termination to further assist in thereduction of corona losses or electrical brush discharge.

The condensers of this invention have been found to be capable ofstanding continuous operation in high frequency rectifier service atvoltages in excess of 50,000.

This invention will best be understood by referring to the accompanyingdrawing in which:

Fig. 1 is a longitudinal section of a condenser of this invention; alsothe showing of the telescoping of other similar adjacent condensers.

Fig. 2 is a cross section view taken on line 2-2 of Fig. 1.

Fig. 3 is a circuit arrangement of the series connection of thecondensers of Fig. 1.

Fig. 4 is a partial longitudinal section of the top end portion showinga method of making a connection between the inner electrode and theouter electrode of an adjacent condenser.

Fig. 4A is a partial elevation of Fig. 4.

Fig. 4B is a partial longitudinal section of a condenser of thisinvention showing another method of making connection to the innerelectrode of a condenser.

Fig. 5 is a schematic showing of a voltage multiplier circuit employingthe condenser of this invention; and

Fig. 6 is a circuit diagram of a voltage multiplier.

Referring now in detail to Figs. 1 and 2 of the drawing, a flask shapeddielectric member I is shown, preferably constructed of boron silicateglass. Such a glass is particularly adapted for high frequency use suchas, for example, Pyrex or Nonex glass. The flask I is provided with are-entrant portion 2. The'reentrant portion .extends substantiallybeyond the center of the flask and is terminated by a dome-shapedconstruction, as indicated at 2. Beyond the domeshaped portion a longnarrow neck 3 is formed.-

A skirt 4 is formed. at substantially the central portion thereof andconnects the outer wall portion of the flask I with the neck portion 3.At the junction of skirt 4 and the outer cylindrical portion l, the wallthickness of the dielectric member is substantially increased inthickness at point 5 and provided with a radius 6 which is suiflcient toprevent corona discharge at the operating voltage of the condenser. Theouter cylindrical portion of flask I (starting at radius 6) and there-entrant portion including dome 2 is coated with a metallic electrode1 which is preferably formed on the glass by applying a thin coating ofsilver paste, and then heating the glass to a temperature suflicient tomelt the silver and unite it with the glass, which temperature is in theorder of 400 to'500 degrees centigrade. The inner portion of flask I isentirely coated with a etallic electrode 8 which is also formed withthen the surplus removed, after which it is heated in a maner mentionedabove in connection with electrode I. Electrode 8 terminates Just shortof the extreme end of the condenser at a point 0. The wall thickness l'is approximately 2 millimeters thick, and when constructed of specialglass for high frequency rectifier use (the condenser being used as afilter condenser) will stand approximately 50,000 volts D. C. at aripple frequency of about 100 kilocycles and carry current in the orderof 200 miiliamperes. It is noted that the increased portion of the wallthickness at point I is curved in three different directions, the firstbeing formed by radius 0, the second by the curved inner wall and thepoint III, which curvature follows substantially the curve of dome 2.The third or outer curvature is formed at point II. This increased wallthickness is located at a point wherethe electrostatic stress of thesurrounding air is normally most intense, and by this construction thestress is considerably decreased so that all tendency of the formationof corona discharge at this point is substantially eliminated. Theprovision of the skirt 4 electrically subdivides the creepage path betwethe outer electrode 1 and inner electrode 0. urthermore, the shape andarrangement of the upper portion of the flask, starting from point 8 andterminating at the radius of curvature 8 on the inner portion of skirt4, is such that in event an excess voltage is applied, the condenserwill be discharged by an electric are which will form at this point. Theratio of length of this creepage path and the wall thickness of theglass is such that the arc will discharge before the voltage is built upsuificiently to puncture through the glass wall. In one form ofcondenser which was constructed in accordance with this invention, thetotal length of the flask was about inches long, 2 inches in diameter atthe outer portion of the fiask, 1% inch at the re-entrant portion, and1% inch at the neck portion, the outer diameter of the skirt being 3inches in diameter and the wall thickness approximately .784 or about 2millimeters thick. The curvature of radius 6 was equal to about V; of aninch. Such a, condenser has a capacity of 500. micromicrofarads and will.stand 50,000 volts. The cost of a condenser of this type is about onequarter of an equivalent prior art type of the same capacity and voltagerating.

As shown in Fig. 3, the condensers of Fig. 1 are teiescoped andconnected in series, the connection from the inner electrode 8 beingformed by placing a flexible metallic member I! over the inside metalliccoated wall of the re-entrant dome portion 2. This connection I! may beformed of spring metallic material or flexible "Belden or strandedcopper braid which, as shown by Fig. 1, extends beyond the end of neckportion 3 and terminates in a flexible band I! and is soldered thereto.The other end is located at and extends beyond the metallic base of domeportion 2. The outer electrode 1 is connected by a split band clamp llwhich clamp may also form a supporting base to be secured to aninsulator IS, the clamp It being secured to'insulator Ii by means of abolt It. In order to provide intimate contact between clamp 4 andelectrode I, a soft lead gasket i1 is provided. Likewise, if desired, asoft gasket I! may be interposed between electrode 'l of the adjacentcondenser and member II. The two ends of the band clamp II are clampedtogether by means of bolt is and nut 20.

Fig. 4 shows a modified telescoping method {baud a semi-fluid silverpaste which is poured in and "whereby a telescoping placing aresilientsstopper 21' of rubber in the neck of the condenser J2. The

braid I! is carried beyond the' of and clamped by a split end cap Nwhich is constructed of spring metal, such as phosphorous and p isprovided with bent fingers'llA, the arrangement being such that the bentfingers make a good sliding contact with the outside electrode 1 of anadjacent condenser. A screw 12 and nut it retains the end cap inposition.

When a connection other than the series arrangement shown by Figs. 3 and(is desired, an alternative arrangement shown by Fig. 4B is provided.This method is used as a terminus of the end condenser, or when parallelor non-telescoping arrangements of the device as desired. Theconstruction of the terminal electrode of Fig. 43 includes a resilientrubber stopper member IIA having a central aperture therein throughwhich passes a terminal screw A which is provided with a clamp nut A. Inorder to prevent formation of corona at this point and also the entry ofdust or moisture, a spherical shaped metallic member flB is provided.The connection is made by means of a metallic tubing 20. To insurepositive connection between the inner electrode I and terminal screw22A, a soft lead gasket 26 is provided between the glass and rubberstopper. Alsoa metal washer TI is placed beneath the terminal nut 23 todistribute the pressure on stopper II when it is compressed by screw22A.

Figs. 5 and 6 illustrate the improved voltage tripling circuit whereinthe capacitors of this invention are arranged to form a compact circuitstructure with other associated apparatus such as, for example, a highvoltage Tesla coll II which includes a primary winding I connected to analternating current input source IIA which may be that of an oscillatorhaving a frequency of 100 kiiocycles. A high voltage secondary winding82 is located above the primary winding 8i and is supported by an aircore tubular insulating member 30A. The output voltage derived at theterminals of the secondary winding 32 is preferably in the order of 30kilovolts, and as shown in Fig. 5, one side is connected to the cathodeof a rectifier tube 33. The rectifier tube 31 is preferably that of theRCA tube 8016 type. The cathode of rectifier tube 33 is connected to theterminal 248 of condenser iA which is the type shown in Figs. 1 to 4inclusive. is connected to ground. The rectifier voltage between plate"A and ground SIB is approximately 30 kilovolts.

Because the voltage is too high at a point ad- Jacent the rectifier tubeIt and condenser IA to insure sufiicient insulation to the filaments ofthe rectifier, the ordinary filament heating transformer which isgenerally employed in lower voltage rectifier circuits cannot beemployed. Therefore, in order to heat the cathode or filament at thispoint, a. small resonant circuit. sufficient to heat the rectifierfilaments to approximately 200 -miliiamperes, is provided. This circuitincludes The other side of secondary I! tialiy well above the groundpotential indicated at SIB. The transformer 40 i generally tuned to thefundamental frequency. However, if desired, it may be tuned to aharmonic frequency if the harmonic content is sufficient to permitconstant energy to be derived to properly heat the filament of therectifier tube. The current passing through the transformer ll is thecurrent passing through the tube capacitance between anode and filament.As shown in Fig. 6, the filament is connected from one side of coil 40to th tap A. A second rectifier tube I4 is supported by an insulatingtube "A, extending out from the re-entrant portion of condenser IA, andis electrically connected to the outside electrode I by the supportingband I 4 of one of the ca thus keeping the entire radio frequencysubstanpacitors of this invention. The filament or cath ode of rectifierI4 is heated by coil 40 and condenser 4| in the same manner as mentionedabove in connection with the heating of themetifier 83. A thirdrectifier tube 35 also has its anode connected to electrode I ofcondenser IA. At this point, the voltage from rectifier l4 and ground33B is now increased to 90 kilovolts; and there is connected in seriesbetween the anode of rectifier tube it and ground the two condensers IBand IQ of this invention. A connection is made from band ll of condenserIB to the cathode of rectifier 35 and the anode of rectifier 33. Thefilament of rectifier 85 is heated by an autotransformer 40 in thesamemanner mentioned above in connection with rectifier 33, although the tapA may be for a different value of voltage and current. Also, if desired,a different type of rectifier may be employed than the previouslymentioned rectifiers for the reason that the voltage is substantiallyincreased at this point. It will be noted that by the use of condensersof this invention, the structural arrangement of the high voltagecircuit is substantially reduced in physical dimensions over that of thetype wherein ordinary condensers are employed. Also the shape andstructural features of the condensers IA, IB and IC of this inventionpermit complete freedom of design, allowing the condensers to beinterchanged from a series telescoping arrangement to that of a parallelarrangement with a minimum amount of supporting structure.

The mode of operation of the high frequency high voltage source shown byFigs. 5 and 6 is as follows: A radio frequency voltage of approximately100 kilocycles and 30 kilovolts is obtained from the alternating currentgenerated source impressed on the Tesla coil II. The output alternatingcurrent voltage from the secondary 82 is rectified by the firstrectifier 33, which charges condenser IC to a peak voltage E of 30kilovolts. The alternating current generator in series with thecondenser IC charged by rectifier it acts in eflect as the energizingsource for the second rectifier 35, and thus condenser IA is charged toa double voltage 2E of 60 kilovolts Rectifier I4 is energized (goingfrom the plate toward the cathode) by the voltages on condenser IA, thealternating current generator, and the condenser IC in series. As thepolarity of condenser IC is opposing, the total energizing voltage onrectifier I4 is composed of two parts, one part being equal in magnitudeto 2E (due to the voltage on condenser IA plus the voltage of thealternating current generator), and the other part in an opposing sense,a minus voltage E (on condenser IC) efiectivel producing a voltage E oncondenser IB. With respect to ground,'-fiowever, the

a cathode of rectifier 84 is at triple potential, or has a voltage SE ofkilovolts. The filament heating auto-transformer ll receives its currentthrough the alternating current generator I. It will be seen that thehigh radio frequency voltage E from the secondary :2 drives a currentthrough the plate-cathode or interelectrode capacitance of the diodesover the respective filter condensers. The radio frequency currentflowing through the rectifier interelectrode capacitance is stepped downby the auto-transformer winding 40 which together with the smallvariable condenser H is brought into resonance to obtain the propervalue for heating the filament of the rectifiers.

This invention is not to be construed as limited to the modificationsdescribed.

What is claimed is:

1. An electric condenser comprising a hollow member and a metallicelectrode coating on a portion of the outside wall of said dielectricmember.

2. A high electrostatic condenser comprising a hollow cylindricaldielectric member having anentrant portion and a neck portion of reduceddiameter located above said re-entrant portion, the reduced diameter ofsaid neck po tion being such as to permit telescoping of a si ilarcondenser at the re-entrant portion of said similar condenser, ametallic electrode coating on substantially the entire inside wall ofsaid dielectric member and a metallic electrode coating on a portion ofthe outside wall of said dielectric member.

3. A high voltage electric condenser comprising a glass cylindricalflask having a re-entrant portion extending substantially midway in saidfiask, a neck portion having a width such as to permit telescoping of asimilar condenser at the re-entrant portion of said similar condenser, ametallic electrode coating on substantially the entire inside wall ofsaid flask, a metallic electrode coating on the outside wall of there-entrant portion of the outside wall and terminating substantiallymidway on said flask and a thickened glass portion located at thetermination of said outside electrode. 7 4. A high voltage electriccondenser comprising two cylindrical walls of dielectric material. saidcylindrical walls being connected together at the lower portion thereof,the innermost cylindrical wall being terminated by a dome portion. theoutermost cylindrical wall having a skirt portion forming a coronashield for said condenser, a metallic electrode coating on the entireinside wall .of both of said cylindrical walls and a metallic electrodecoating on the outside wall adjacent said skirt of the outermostcylinder, and the outside wall of said innermost cylinder, includingsaid dome portion.

5. An electric condenser arrangement for a high frequency voltagemultiplier circuit comprising a plurality of rectifiers of the electrondischarge device type and a plurality of condenser elements having acylindrical dielectric member with a re-entrant portion, a metallicelectrode on the inside walls, a metallic electrode coating on a portionof the outside walls of said dielectric member and at least two of saidconwithin the re-entrant portion of an adjacent condenser.

'densers connected in series by a connection made 6. An electriccondenser arrangement for a" high frequency voltage multiplier circuitcomprising a plurality oi rectifiers of the electron discharge devicetype and a plurality of -condenser elements havinra cylindricaldielectric "member with a 're-entrant portion and a long neck portion, ametallic electrode coating on the inside walls of said cylindricaldielectric member. a metallic electrode coating on a portion of theoutside walls of said cylindrical dielectric member, and means toprovide a connection irom element having a cylindrical dielectric memberwith oppositely disposed neck and re-entrant portions. said re-entrantportion extending to a point intermediate the ends of said condenserelement. the width of said neck portion being such as to pennit theteleswping of a similar condenser element at the re-entrant portion ofsaid similar condenser element, a metallic electrode on the inside wallof said dielectric member, a metallic electrode coating on the outsidewall of said reentrant portion and on a portion of the outside wall ofsaid condenser, a skirt portion located at the termination of thecoating on the outside wall of said condenser to form a corona shield toprevent brushing between the inside and outside electrodes.

8. An electric condenser arrangement for high irequency and high voltageuse comprising a plurality of condenser elements having cylindricalre-entrant portions, a metallic electrode on the inside wall of saidcylindrical dielectric elements. a metallic electric coatingvon aportion oi the outside wall of said dielectric elements, supportingmeans for said condenser elements, the arrangement being such thatadjacent condenser elements telescope within the re-entrant portion soas to provide variation in capacity between adjacent condenser elements.

condensers being arranged to support some of said rectifiers and meansto heat the filaments of said rectifier by a transformer tuned to theresonant frequency of the input source of said rectifier circuit.

11. A high voltage rectifier circuit including a high voltageoscillation circuit. a plurality of rectifiers connected to saidoscillation circuit, a plurality of condensers of the type having acylindrical fiask with a re-entrant portion with inner and outerelectrodes, a transformer surrounding and supported by the'base of saidrectifiers to heat the filaments thereof by being tuned to the resonantfrequency of said oscillation circuit, and a a plurality of condensersof said first mentioned a e s:

a I form a voltage divider between the output of said rectifier circuitand ground.

12. A high voltage rectifier circuit including a high voltageoscillation circuit, a plurality oi rectifiers connected to saidosicllation circuit, a plurality oi condensers of the type having acylindricalfiaskwithare-entrantportionwithinner andouter electrodes, atransformer surrounding and supported by the base oi said rectifiers anda variable condenser supported by the base of said rectifier tubes toheat the filaments thereof by being tuned to resonant frequency of saidoscillation circuit and a plurality of condensers connected together inseries to form a voltase divider between the output of said rectifiercircuit 13. a high voltage rectifier circuit including in alternatingcurrent input source, a rectifier of the type having a filament and aninsulating base, means including an inductive element which is securedto and surrounds said insulating base which is connected to saidfilament to heati filament of said rectifier, said inductive elementbeing tuned substantially to the resonant frequency oi the input sourceof said 'rectifiercircuit.

14. A high voltage high frequency rectifier circuit including arectifier of the type having a filament,,a condenser of the type havinga reentrant portion; said rectifier being insulatingly supported by.electricall connected to and located adiacent said condenser at there-entrant portion thereof; inductive means to heat the filament of saidrectifier; and means capacitively and cooperatively associated with saidinductive means to tune said combination substansource of said highvoltage high frequency.

15. A high voltage high frequency rectifier circuit comprising analternating current input source, a tube having a base. said tube beingenergiaed by said alternating current, a transformer mounted on saidbase and having a winding positioned in the neighborhood oi said base,and a condenser connected in shunt with said winding for tuning saidtransiormer.

16. In a high voltage high frequency rectifier circuit, a plurality ofrectifiers, a plurality of condensers. at least one of said condensersbeing of the hollow cylindrical type having a neckportionandare-entrantportion,afirstoneoisaid rectifiers insulatinglysupporting one end of said one condenser at said neck portion, a secondrectifier insulatingly supporting the other end of said one condenser atan end opposite said neck portion, and a third rectifier insulatinglysupported at one end by said one condenser at the re-entrant portion,the other endof said third rectifier being insulatingly supported by atleast another condenser.

17. A high voltage rectifier circuit operable to rectify currents havinghigh frequency components including a rectifier of the type having ananode and a filament with inter-electrode capacity therebetween, meanstuned to resonate at the high frequency components including anautotransiormer having an inductive winding and shunt capacitance, saidwinding including a tapped portion to heat the filament of saidrectifier, said transformer winding and shunt capacitance being tunedsubstantially to the resonant frequency of the input source of saidrectifier circuit, means connecting the transformer winding in serieswith the rectifier anode-filacondenser type connected together in seriesto II ment inter-electrode capacity whereby, the high and meansconnecting said filament; to the tapped portion of the inductivewinding.

18. A high voltage rectifier circuit for rectifying high frequencycomponents including a rectiher of the type having an anode and afilament with inter-electrode capacity therebetwee'n, a parallelresonant circuit including an inductance and capacitance tuned to thefrequency of the applied high frequency components, means connecting theparallel resonant circuit in series with the high frequency componentsthat are applied to the rectifier whereby the high frequency componentstransmitted by the inter-electrode capacity of the rectifier areeffective to energize the tuned circuit. and means connecting thefilament of the rectifier across at least a portion of the inductanceelement of the tuned circuit to thereby energize the filament.

19. A high voltage circuit operable to rectify currents having highfrequency components including a high frequency source of energy, arectifier of the type having an anode and a filamentary thermionicelectron emitter, a parallel resonant circuit including an inductanceand a capacitance tuned to substantially the frequency of the highfrequency components, means to apply energy from the high frequencysource across the rectifier in series with the tuned circuit whereby thetuned circuit may be energized due to energy passed by theinter-electrode capacity of the rectifier, and means to connect thefilamentary electrode emitter across at least a portion of the in- 10ductance element of the tuned circuit to supply energy to the filamentof the rectifier in order that the applied high frequency energy may berectified.

O'IIO H. SCHADE.

REFERENCES CITED The following references are of record in the file ofthis patent:

UNITED STATES PA'I'ENTS Number Name 6 Date 454,622 Tesla June 23, 18911,863,477 Gebhard June 14, 1932 1,870,960 Nyman et ai Aug. 9, 19322,028,907 Higgins Jan. 28, 1936 2,045,034 Kuntke June 23, 1936 2,163,218Schlesinger June 20, 1939 2,302,900 Vance Nov. 24, 1942 2,369,772Bouwers Feb. 20, 1945 2,373,165 Cawein Apr. 10, 1945 2,374,499 Quayle eta1 Apr. 24, 1945 2,459,988 Boadle Jan. 25, 1949 FOREIGN PATENTS NumberCountry Date 6,575 Great Britain Mar. 16, 1914 511,126 Germany Oct. 30,1930 576,869 Germany May 18, 1933 660,890 Germany June 4, 1938 OTHERREFERENCES Schade Pub. No. ST-235, April 1943, R. C. A.

